Data Modeling & Database Systems
EXAM QUICK REFERENCE NOTES
ENHANCED ENTITY-RELATIONSHIP (EER) MODEL
1. EER Model Overview
EER extends the ER model to handle complex requirements.
Adds: subclasses/superclasses, specialization, generalization, categories (union types),
attribute & relationship inheritance.
2. Subclass / Superclass
TERM MEANING
Superclass General entity type (e.g. EMPLOYEE)
Subclass Specific subgrouping (e.g. SECRETARY,
ENGINEER)
IS-A SECRETARY IS-A EMPLOYEE; subclass
inherits all superclass attributes &
relationships
1:1 relationship Each entity appears once in superclass
and optionally in subclass(es)
3. Specialization vs. Generalization
Specialization Generalization
Top-down: Start with superclass, define Bottom-up: Start with entity types, find
subclasses common properties → superclass
EMPLOYEE → {SECRETARY, CAR + TRUCK → VEHICLE
ENGINEER, TECHNICIAN}
EXAM QUICK REFERENCE NOTES
ENHANCED ENTITY-RELATIONSHIP (EER) MODEL
1. EER Model Overview
EER extends the ER model to handle complex requirements.
Adds: subclasses/superclasses, specialization, generalization, categories (union types),
attribute & relationship inheritance.
2. Subclass / Superclass
TERM MEANING
Superclass General entity type (e.g. EMPLOYEE)
Subclass Specific subgrouping (e.g. SECRETARY,
ENGINEER)
IS-A SECRETARY IS-A EMPLOYEE; subclass
inherits all superclass attributes &
relationships
1:1 relationship Each entity appears once in superclass
and optionally in subclass(es)
3. Specialization vs. Generalization
Specialization Generalization
Top-down: Start with superclass, define Bottom-up: Start with entity types, find
subclasses common properties → superclass
EMPLOYEE → {SECRETARY, CAR + TRUCK → VEHICLE
ENGINEER, TECHNICIAN}
